The invention relates to pipe couplings, and more particularly to the type coupling often used for cast iron soil pipe, wherein an annular elastic gasket is fitted over adjacent pipe ends and tightened down with encircling bands.
A number of clamped band type soil pipe couplings have been suggested and used previously. The typical such coupling utilized a corrugated sheet metal shield with overlapped ends, the shield being immediately circumjacent the elastic gasket band. Surrounding the shield were at least two axially spaced metal clamp bands capable of being tightened down by a wrench or screw driver. The clamp bands were typically tack-welded to the corrugated shield at several locations to retain them in place, both the bands and the shield usually being of stainless steel to resist the corrosive influences associated with soil pipe. Couplings of this type are shown in U.S. Pat. Nos. 3,233,922 and 3,359,017.
Although these couplings have in general been effective, they are relatively costly to produce, particularly in light of the large amount of stainless steel required for the corrugated shield and also because of the required tack-welding operations. Also, the overlapped corrugations of the shield ends sometimes caused an undesirable frictional resistance to tightening, since the corrugations of the two ends were being tightly pressed together during tightening.
No previous coupling of this type has been as efficient in operation and as economically manufactured and easily assembled as the present invention described below.